Index of Refraction (n = c/v)

Also known as refractive index

n = \frac{c}{v}

n =

v =

Enter your known values, leave one input blank, and solves for the missing one. Try different units for next level excitement!

Constant used — built into this formula, no need to enter

c = 299,792,458\ \text{m/s}

Speed of light in vacuum · exact

Learning zone

The refractive index is simply a speed ratio, with c = 299 792 458 m/s in the numerator. In water (n = 1.333) light travels at about 2.25 × 10⁸ m/s; in diamond (n = 2.42) it crawls at 1.24 × 10⁸ m/s. The large index is what gives diamond its fire: the stronger the slowdown, the harder light bends and the more tightly it can be trapped by total internal reflection inside the cut facets.

Index of Refraction (n = c/v)

n = \frac{c}{v}

Where

$n$ = Index of refraction
$v$ = Speed of light in the medium

Missing one of these? Work it out first, then come back

Index of refraction — Apparent Depth, Snell's Law of Refraction
Speed of light in the medium — Speed, Distance & Time, Kinetic Energy

Part of this formula set

Refraction and total internal reflection

5 formulasSnell's law and the refractive index, with the critical angle, Brewster's angle and apparent depth that follow from bending light at a boundary.